Synthetic, structural, electrochemical and solvent extraction studies of neutral trinuclear Co(ii), Ni(ii), Cu(ii) and Zn(ii) metallocycles and tetrahedral tetranuclear Fe(iii) species incorporating 1,4-aryl-linked bis-β-diketonato ligandsCCDC reference numbers 665749 and 665750. For crystallographic data in CIF or other electronic format see DOI: 10.1039/b716653bElectronic supplementary information (ESI) available: Cyclic voltammograms for H2L1 (R = t-Bu) together with those for [Co3(L1)3(Py)6] (R = t-Bu), [Ni3(L1)3(Py)6] (R = t-Bu) and [Zn3(L1)3(Py)6] (R = t-Bu); representative plots for the extraction experiments; tables of selected bond lengths and angles. See DOI: 10.1039/b716653b

Uncharged complexes, formulated as trimeric metallocycles of type [M3(L1)3(Py)6] (where M = cobalt(ii), nickel(ii) and zinc(ii) and L1 is the doubly deprotonated form of a 1,4-phenylene linked bis-β-diketone ligand of type 1,4-bis(RC(O)CH2C(O))C6H4 (R = t-Bu)) have been synthesised, adding to related, previously reported complexes of these metals with L1 (R = Ph) and copper(ii) with L1 (R = Me, Et, Pr, t-Bu, Ph). New lipophilic ligand derivatives with R = hexyl, octyl or nonyl were also prepared for use in solvent extraction experiments. The X-ray structures of H2L1 (R = t-Bu) and of its trinuclear (triangular) nickel(ii) complex [Ni3(L1)3(Py)6]·3.5Py (R = t-Bu) are also presented. Electrochemical studies of H2L1, [Co3(L1)3(Py)6], [Ni3(L1)3(Py)6], [Cu3(L1)3], [Zn3(L1)3(Py)6] and [Fe4(L1)6] (all with R = t-Bu) show that oxidative processes for the complexes are predominantly irreversible, but several examples of quasireversible behaviour also occur and support the assignment of an anodic process, seen between +1.0 and +1.6 V, as involving metal-centred oxidations. The reduction behaviour for the respective metal complexes is not simple, being irreversible in most cases. Solvent extraction studies (water/chloroform) involving the systematic variation of the metal, bis-β-diketone and heterocyclic base concentrations have been performed for cobalt(ii) and zinc(ii) using a radiotracer technique in order to probe the stoichiometries of the respective extracted species. Significant extraction synergism was observed when 4-ethylpyridine was also present with the bis-β-diketone ligand in the chloroform phase. Competitive extraction studies demonstrated a clear uptake preference for copper(ii) over cobalt(ii), nickel(ii), zinc(ii) and cadmium(ii). [ABSTRACT FROM AUTHOR]